Brake



Nov. 12, 1935.

.1. c. WAHL BRAKE gmc/who@ l0 wa C 6 m @m ON Q Nm. wm Om. vv 6% J. C.`WAHL Nov. 12, 1935.

BRAKE Filed Nov, 8, 1955 5 Sheets-Sheet 2 loo gmc/who@ c/dmes C. Wd// J.C. WAHL Nov. l2, y1935.

BRAKE Filed Nov. 8, 1933 5 Sheets-Sheet 3 mm. www N NOV. 12, 1935. J, C,WAHL 2,020,667

BRAKE Filed Nov. 8, 1933 5 Sheets-Sheet 4 Nov. 12, 1935. J, Q WAHL2,020,667

BRAKE Filed Nov. 8, 1953 5 Sheets-Sheet 5 328 dan-796 I Wel/1l Oft/hmmm;

Patented Nov. 12, 1935 IUNITED STATES PATENT oFFlcE BRAKE James C. Wahl,Akron, Ohio, assig'nor to Wingfoot Corporation, Wilmington, Del., a.corporation of Delaware This invention relates to brakes and ,moreparticularly to hydraulic brakes adapted for use von airplanes and othervehicles in which tires of large cross-sectional and small beaddiameters are ordinarily employed which fit directly upon a relativelysmall supporting hub or wheel.

It is an object of the present invention to provide a simple, effectiveand long-wearing brake for use with a hub or Wheel of relatively smalldiameter.

Another object of the invention is the provision of an improvedhydraulic brake which employs a minimum of wearing parts to produce amaximum -of braking power and efficiency.

Another object of the invention is to provide a brake for a tire mounteddirectly upon a rotatable hub.

Another object of the invention is to provide a disc-type hydraulicbrake for super balloon or cushion tires, which brake is particularlyadapte'i for airplane or similar installation, being light in weight,positive in action and long-wearing in use. r

Another object of the invention is the provision of a brake which isparticularly designed to be associated with an inflated rubber tire andtube with the brake positioned and arranged to be cooled vby radiationand by the ow of air over the braking surface without damage by heat `tothe tire and tube.

Another object of the invention is the provisich of a vehicle brakewhich has a minimum of parts and which can be readily assembled andtaken apart and in which wear and breakage is reduced to a minimum.Thebrake parts are made as far as possible in unitary integral form sothat machining, finishing and assembling and repair are readilyaccomplished.

Another object of the invention is the provision of an improvedhydraulic brake in which uniform braking tension is applied over theentire braking surface by means which are simple, long-wearing andpositive in action.

Another object of the invention is to provide a fluid brake With animproved piston construction having a materially larger fluid engagingsurface than those heretofore used or possible in fiuid brakes wherebythe working pressure in the system can be considerably reduced withoutsacrificing ultimate braking pressure. Weight and cost of the fluidsystem are reduced and in addition the muscular effort, on the part ofthe operator, necessary to effect a braking action is decreased.

Another object of the invention is to provide a ThusI hydraulic vehiclebrake in which the lubricated and wearing parts are completely protectedfor allpractical purposes from dirt, grit or other foreign matter.

Another object of the invention is to provide a 5 brake assembly inwhich the braking action is transmitted directly to the tire without anyintermediate wearing or strain receiving or carrying parts.

The foregoing and other objects of the inven- 10 tion are achieved bythe mechanisms described hereafter and illustrated in the accompanyingdrawings, wherein:

Fig; 1 is a longitudinal vertical cross-sectional view, taken on lineI-I of Fig. 2, of one form of 15 the invention;

Fig. 2 is a transverse diametrical cross-sectional view taken on lineII-II of Fig. 1;

Fig. 3 is a longitudinal cross-sectional View similar to Fig. 1, andtaken on line III-III of 20 Fig. 4, of a second form of the invention.

Fig. 4 is a diametrical cross-sectional view taken on line IV-IV of Fig.3 and similar to Fig. 2;

Fig. 5 is a longitudinal cross-sectional view of 25 still another formof the invention.

Referring to Figs. 1 and 2 of the drawings, the numeral I0 indicates afixed or a non-rotatable axle upon which is journaled a rotatable hub I2through the agency of suitable bearing means 30 such as those indicatedat I4 and I5. An anchor bracket I6 is secured by any desired means (notshown) at the Ainboard or supported end of the axle Ill and this bracketserves as a means against which the inboard bearing I4 can be abuttedwith 35 the outboard bearing I5 being held in place by a locking collarI8, which is secured on the outboard or cuter end of the axle I0 bymeans such as a bolt 20 which extends dlametrically through the collarI8 and through suitable slots 22 in 40 the end of the shaft I0.

Completing the assembly of the outboard end of the brake is a tireretaining flange 26 which is secured in place against the hub I2 bysuitable means Which may take the form of stud 45 bolts 28 and nuts 30,which are positioned at spaced points around the circumference of theflange 26. As will be seen from the drawings, the tire-retaining flange26 is formed with a radially inwardly extending portion 32 which is 50adapted to fit down closely adjacent the collar I8 and ordinarily gasketmeans, such as those shown at 36, are provided between the collar andthe inwardly extending portion 32 in order to seal lubrication in aroundthe bearing I5. lili It will also be noted from the drawings that thetire-retaining ilange 26 is provided with a beveled portion at itsinboard side which cooperates with a beveled end portion of the hub I2,as indicated at 38. By this arrangement of 'parts the tire-retainingflange and the hub I2 are positively aligned in an axial direction onassembling, as is necessary for a proper operation of the tire wheel andbrake unit. The` tire-retaining iiange 26 is also formed with acylindrical surface 46 which forms a support or engaging surface for theoutboard bearing I5. Some suitable cover or hub cap is ordinarilyprovided, such as that shown at 44, which completely covers the end ofthe assembly and which may be secured to the outer periphery of thetire-engaging flange 26 by means which may comprise screws 46.

The brake unit proper is mounted at the inboard end of the hub I2between the anchor bracket I6 and an enlarged bell-like portion 56formed preferably integral with the hub I2. The brake unit consists of aplurality of braking discs 52 which are adapted to be axially keyed tothe bell-like portion 56 of the hub I2 as, for example, by providingradially extending tongues or lugs 54 on the discs which are received incooperating axially extending grooves 56 formed in an anchor ring 58which is secured as by rivets 66 to the bell portion 56. to support thediscs is a distinct improvement over former practices of securingbraking discs directly to a supporting member inasmuch as it is possibleto make the ring of hardened metal which can be more readily andaccurately machined so that any tendency for the lugs 54 to cut into thegrooves 56 to prevent free axial movement of the discs is substantially'eliminated. The braking discs l are preferably provided withcircumferentially extending and radially extending slots 62 which allowfor expansion of the braking discs in use without buckling or binding ofthe braking parts.

Cooperating with the braking discs 52 are a plurality of interposedbraking plates 64 which are axially keyed to the anchor bracket I6through the agency of keys 68 which are secured in axially extendinggrooves 'I6 at circumferentially spaced points on the anchor bracket I6.Suitable slots 1| are provided in the braking plates 64 for thereception of the anchor keys 68 so that the plates can have axial butnon-rotative movement on the anchor bracket I6. The keys 68 can befastened to the anchor bracket with rivets 12 or like means, if desired.

Positioned at the outboard side of the interposed braking discs 52 andbraking plates 64 is an abutment or shoulder plate 'I4 which isadjustably positioned on the anchor bracket i6, as`

by providing cooperated threaded portions indicated at 16. A lockingring 'I8 having ends received in an axially extending groove 86 may beemployed to lock the abutment or shoulder plate 14 in the desired axialposition on the anchor bracket I6. It will be appreciated that thisshoulder plate I4 can be adjusted in an axial direction initially orafter use to provide an adjustable take-up or a certain initial pressureon. the braking plates and discs.

The fluid pressure applying means forming a part of the brake unit arepositioned at the inboard sideof the braking discs and plates: and arecarried by any suitable supporting means which preferably take the formof an integral radially extending ilange 84 formed on the anchor bracketI6. The flange 84 is provided with The use loi an anchor ring 58 anoutwardly facing channel 88 which receives' a piston 88 for axiallyreciprocable movement. It will be noted that by making the piston ringshaped and having it surround the axle it is provided with aconsiderably larger uid con- 5 tacting area so that the pressure in thesystem can be reduced as can the muscular eilort required to eiect abraking action. The piston 66 is formed with a laterally extendingshoulder or ridge 66 which extends into engagement with a 10 pressureplate 92 which engages with the inboard side of the superimposed brakingdiscs and plates. Means are preferably provided' to hold the pressureplate 92 at 'its non-clamping position and to this end axially extendingre- 15 cesses 94 may be formed at circumferentially spaced points in theanchor bracket I6. Springs 96 are placed in these recesses 94, whichsprings bear at their outboard end against the shoulder plate 14 with around headed rivet 98 or the like 20 being placed therebetween. asillustrated in Fig.

1, to allow adjustment of the shoulder plate 14 without binding actionon the spring 66. The inner ends of the springs 96 bear against radiallyinwardly extending lugs |66 formed integral with 25 the pressure plate82 and the operation of parts is such' that the expanding action of thesprings normally retains the pressure plate 92 and piston 88 innon-clamping position. 'I'his axial positioning of a plurality ofsprings is a. novel fea- 80 ture of design which economizes space andwhich correlates well with the clamping action of the piston.

The uid pressure means for operating the plston 88 preferably take theform of a ring gasket 85 |64 which is U-shape in cross-section toprovide axially extending ange-like lips |66 which lie against the innerand outer circumferential cylindrical walls of the channel 86. In orderto positively hold the flange lips |66 of the rim 40 gasket |64 inpositive engagement at all times, spring rings |68 and .I I6 areemployed. The spring ring I 68 is an expanding ring and is undercompression while the spring ring I|6 is a compressing ring undertension. Conduit means 45 (not shown) are adapted to extend to thechannel 86 at the back of the ring gasket |64 and for this purpose aplurality of axially extending bosses I I4 may be formed integral withthe flange 84. The bosses I I4 are tapped to receive the con- 50 duitsfrom the fluid pressure source and serve to conduct the fluid underpressure directly to the back of the gasket ring |64. A plurality ofbosses are provided in order to allow the brake and wheel assembly to beemployed in various 55 relations with the most accessible connectionboss being employed for the pressure conduit.

It will be understood that any suitable pressure fluid can be employedin the system lsuch as oil.

However, the invention likewise contemplates the 60 use of air which,due to its weight, would be particularly adapted for use in the systemwhen employed with aircraft.

Means are provided to hold the lubricant around the inboard bearing I4and away from 65 the braking plates and discs and to this end a ringplate I I6 may be secured as by screws II8 to the hub I2, as shown inFig. 1. Gasket means |26 of suitable character are carried by the ringI|6 and engage with the anchor bracket I6. Sealing means are likewiseprovided at the end of the bell portion 56 of the hub I2 to protect thebraking plates and discs against foreign matter and these sealing meansmay comprise a gasket ring 222 which is positioned between the outerperiphery of the flange 84 and the inside of the inboard end of the bellportion 50. A further sealing plate |24 is preferably positioned at theouter side of the piston 88, which plate has axially extending flangesreceived in grooves |26 and |28 formed in the radial flange 84 ofthe'anchor bracket I6.

An air escape valve |30 is provided at the upper side of the flangeportion 84 and a passage |32 extends therefrom to the back of the ringgasket |04. This escape valve |30 is opened when the fluid to be placedunder pressure is initially installed in the system and allows theescape of air. The valve is then closed and remains closedfor the lifeof the assembly unless replacement of the braking and pressure fluid isnecessary.

A feature of the invention is the particular mounting of a tire such asthat shown at |40 directly upon the hub I2 and the retaining flanges 26and 50. The tire is iniiated by the usual inner tube |42 which functionsto force the bead portions of-the tire tightly against thetire-retaining flanges. The gripping relation or bond between the beadsof the tire and the hub and flanges can be increased if cooperatinglocking ribs and grooves |44 are formed on the contact surfaces of thetire beads and the retaining flanges.

In the embodiment of the invention illustrate in Figs. 2 and 4, thenumeral 200 indicates an axle upon which is journaled a hub 202 throughthe agency of suitable bearing means such as the roller bearings 204 and206. At the inboard side of the axle 200 an anchor bracket 208 issecured by any suitable means (not shown). The anchor bracket 208 servesas a stop against which the inboard bearing 204 is clamped with theoutboard bearing 206 being secured on the axle 200 by a collar 2in whichis adjustably locked in position as by a cotter pin 2|2. As willbe seenfrom the drawings, the collar 2| 0 secures the bearings 204 and 206 andthe hub 202 into a compact unit due to the engagement of the bearingmeans with suitable shoulders on the hub 202 and with the inboardbearing 204 being clamped against the anchor bracket 208.

Means such as a sealing ring 2M are secured at the outboard end cf'thehub 202 in order to seal lubricant around the outboard bearing 206. Thesealing ring 2 4 carries the packing 2 I6 which engages with the collar2 0 as illustrated in Fig. 3. A removable tire-retaining flange 2|8 issecured as by a locking ring 220 at the outboard end of the hub 202, anda cover plate 222 is preferably Cil provided over the outboard side ofthe assembly. The cover plate may be fastened in place by screws 224which extend through the outer circumference `of the cap v222 and intothe bead-retaining flange 2 8.

At the inboard side of the hub 202 is mounted a bell-like tire-retainingflange 226 which is removably keyed to the hub as, for exampleL by alocking ring 228. A sealing plate 230 secured to the inboard end of thehub 202 functions to seal lubricant around the inboard bearing 204 inthat a packing element 232 carried by the .sealing plate 230 extendsinto sealing relationship with the anchor bracket 208. Aretaining ring234 secured to the bell-like tireretaining flange 226 may be employed tosecure the locking ring 228 and the sealing plate 230 in properposition.

A plurality of braking discs 236 are carried by the bell-liketire-retaining flange 226, and to this end a mounting ring 238 issecured to the inner end of the bell-like tire-retaining flange 226 bysuitable means such as rivets 240. The mounting ring 238 is formed withaxially extending, circumferentially spaced groo es 242 which receiveradially extending lugs 244 formed on the circumference of the brakingdiscs 236 so that the braking discs can have relative axial movement 5with the bell-like tire-retaining flange 226, but will be carriedthereby without any opportunity for relative rotary movement.Cooperating with the braking discs 236 are a. plurality of interposedbraking plates 248 which are mounted for relative axial movement, butnon-rotative movement, upon the anchor bracket 208. This is accomplishedby providing radially inwardly extending lugs 250 upon the braking,plates 248, which lugs are received in suitable axially extendinggrooves 252 formed at circumferentially spaced points on the anchorbracket 208.

Anadjustable abutment or shoulder plate 256 is provided between theoutboard side of the braking plates and discs andthe hub proper. Theshoulder plate 256 is internally threaded and vcooperates with athreaded end portion as at 258,

bracket 208 is formed with a channel 204 which 30 is adapted to slidablyreceive a piston 266. A ring gasket 268, which is C-shaped or U- shapedin cross-section, is provided behind the piston 266 as illustrated. inFig. 3. An expanding spring ring 210 and a contracting spring ring 212are preferably employed in conjunction with the U-shaped sealing ring268 in order to positively hold and force the legs or lips of thesealing ring into tight engagement with the walls of the channel Thepiston 265 is formed ordinarily with a shoulder 2M which extends intoengagement with a pressure plate 216, which actually forms one of thebraking plates, and which serves to uniformly apply the pressure fromthe piston 266 to the superimposed braking discs 236 and braking plates248. Sealing means such as the shield 280 are provided on the pressureplate 2'1'6, which means extend into a suitably shaped groove 282 formedon the inboard side of the bell-like tire retaining flange 226. A gasket284 may likewise be provided at the inner portion of the shield 280,which gasket extends into sealing relation with the anchor bracket 208.The shield 280 and gasket 284 function to prevent the entrance offoreign `material int(` the interposed brakingf plates and discs.

Some suitable means are preferably provided for holding the piston 266normally in a nonclamping position, and these means may take the form ofa spring spider 286, which spider is adjustably mounted upon a nut 288which screws on the anchor bracket 208 with a locking wire or ring 290being employed to secure the spring spider 286 in the desired adjustedposition.

Similar to the embodiment of the invention illustrated in Figs. l and 2anddescribed above, the present embodiment of the invention is providedwith an escape valve 292 which is in communication with the channel 264so that air can be allowed to escape from the uid system when the fluidis initially placed in the system. Hy- .draulic pressure is appliedbehind the piston 250 `and ring gasket 268 in any suitable manner.However, these means ordinarily take the form sov of conduits (notshown), which extend through suitable bosses formed in the anchorbracket 208, which bosses are tapped and which have passages extendingtrgAahe channel 264.

As illustrated in Fig. 3, a tire 294 is normally mounted directly uponthe hub 202 with the usual inner tube 296 being employed to inflate thetire. In order to prevent any relative movement between the tire 294 andthe retaining flanges 2| 8 and 226, the contacing portions oi the tirebeads and flanges may be formed with inter-engaging grooves and ribssuch as indicated at 293.

In the form of the invention shown in Fig. 5, the brake and wheelassembly is particularly designed for somewhat larger bead diametertires and more definitely for large cross-sectional tires of the superballoon or super cushion type, such as employed on airplanes. Theassembly is, however, not limited to this use but can be employed inland and other vehicles wherever a wheel and brake assembly of this rsimilar design is found desirable.

More specifically, the numeral 300 indicates a fixed axle having atapered periphery which is adapted to journal a wheel, indicatedgenerally at 302, having a hub portion 324 which is journaled on theaxle 300 by an inboard bearing 306 and an outboard bearing 308. The hubportion 304 of the wheel 302 is provided with suitable shoulderedportions which position the bearings 306 yand 308, with the assemblybeing clamped on the tapered axle 300 through the agency of a retainingnut 3|0.

A hub cap 3 I4 is secured as by screws 316 over the end of the axle tocomplete the outer cndp! ,the axle assembly. The wheel 302 is of anydesired form but is preferably a cast or pressed wheel having an'integral drop center rim 3|8 at its outer periphery. The drop centerrim.3l8 is formed with a cylindrical flange portion 320 which serves tosupport a plurality of breaking discs 322 for non-rotative but axiallyslidable movement therein. To this end a supporting ring 324 may beprovided, which ring has a plurality of axially extending channels 326formed therein which receive radially outwardly extending lugs 328formed on the braking discs 322. The ring 324 may be secured as byrivets 330 to the cylindrical ange 320.

An anchor bracket 3l2 is secured by suitable means (not shown) to theaxle 600 and comprises a cylindrical portion 332 which functions tosupport a plurality of'braking plates 334 which are in interposedcooperating relation with the braking discs 322. The braking plates 334are mounted for non-rotative but axial movement on the cylindricalportion 332 of the anchor bracket 3I2 and-this arrangement of parts maybe accomplished as by providing radially inwardly extending lugs 336 onthe plates 334 which are received in axially extending grooves 338formed at circumferentially spaced positions upon the cylindricalvportion 332 of the anchor bracket 3I2.

Positioned between the wheel 302 and the cooperating braking discs andplates is a shoulder plate 340 which is preferably threaded as at 342 onthe cylindrical portion 332 of the anchor,

bracket 312. A lock ring 344 is employed to lock the shoulder plate 340in the desired initial or take-up position. The anchor bracket 3|2 isformed with a circumferential outboardly-facing, channel 350 whichslidably receives a ring piston 352 which vis backed by a ring gasket354 Ibracket; 3|2 over the channel 350.

which is U-shaped in cross-section. The lips of the U-shaped ring gasket354 are urged into tightly engaging relation with the walls of thechannel 350 by an expanding spring ring 356 and a tensioned spring ring358.

The piston 352 engages through a pressure plate 360 with thesuperimposed braking discs and braking plates, with a suitable sealingcover 362 being employed between the piston 352 and the pressure plate360, which sealing plate has 10 axially extending flanges that arereceived in. czgperating grooves 364 in the anchor bracket Additionalsealing means to protect the braking discs and plates from foreignmaterial may comprise a cover plate 366 which issecured at its outercircumference to the drop center rim 3| 8 with suitable gasket means 366being positioned at the inner circumference of the plate 366 which sealagainst the anchor bracket 312. Conduits (not shown) from pressuresources may extend to tapped bosses 310 formed on the anchor In a mannersimilar to that described heretofore in conjunction with the embodimentof the invention illustrated in Figs. 1 to 4, an escape valve 312 isordinarily incorporated in the wheel and brake assembly. If desired, anouter cover plate 316 may be included in the assembly to cover theoutboard side of the wheel.

It is believed that the operation of the various brake mechanisms willbe4 apparent from the foregoing description. Suffice it to say that in Iall of the assemblies the rotation of the wheel or hub upon the xed axlewill cause the braking discs carried by the wheel or hub to be carriedtherewith while the braking plates remain stationary upon the anchorbrackets which are secured to the axle. As long asv the pressureapplying pistons are not forced outwardly by `the interposed brakingdiscs and plates can be forced into engaging relation with each other toeiect positive braking action by applying fluid pressure behind thepistons and sealing ring gaskets to force the discs and plates againsteach other and against the adjustable abutment shoulder.

In all forms of the brake the abutment or shoulder positioned betweenthe wheel or hub and the braking discs can be adjusted to bring theinterposed braking discs and plates into the proper relation after wear.The abutment shoulder also can be initially positioned to properlycooperate with the pressure applying piston so that there will be nodrag on the wheel or hub when no iluid pressure is applied to achievebraking action. A

It will be appreciated that the braking plates an'd discs can be ofvarious materials such as 65 -metal or fiber or like substances and thatthe superimposed plates and discs can be run dry or with a lubricant, asdesired. It has been found, however, that making the plates for exampleof steel and the discs of bronze, land running the brake dry, givesexcellent results.

By the present invention a brake has been provided in which the numberof parts has been reduced to a minimum with the parts beingdesigned sothat they can be readily produced by commercial practices in productionquantities. The assembly is simple and positive in operation and meansare provided to readily take up wear of the braking elements. Theassemblies are of a nature which allows them to be applied to variousnew or used wheel assemblies with little or no modification thereof. Themechanisms of the present invention are positioned at one side of thehub or wheel so that the heat generated from the brake can be readilydissipated by radiation by the cooling action of air flowing over thebrake. Thus the chance for heat from the brake seriously affecting thelife of the tire or its inner tube is materially reduced.

The brake and wheel assemblies herein described are designed to be longwearing in use and to have a minimum of replacement parts.

,The superpressure piston, when applying the braking pressure, appliesthe same uniformly over a complete circle andV with a reduced pressurein the system without sacrificing braking force, gasket means beingemployed of the nature to insure no leakage of pressure of iiuid in useand in which the necessity of a closed pressure bag with its undesirablefeatures is eliminated. Likewise, the braking discs are designed topermit expansion and contraction without buckling and the various partsare formed solid and integral wherever possible, thereby reducing thenumber of parts and corresponding wear, rattle, etc.

While one of the brake mechanisms comprising the present invention hasbeen particularly illustrated and described in conjunction with wheelassemblies adapted to mount a super cushion tire directly on a hub or asmall wheel, it will be 'recognized that the principles of the inventionare readily applicable to braking mechanism for wheel assemblies of alltypes and designs. The brake mechanism may, therefore, be employedwherever it is desired to effect a braking action between relativelyrotatable members.

It will accordingly be appreciated that the present invention is notlimited to details of construction shown in the accompanying drawingsand described above, but that the invention is intended to broadly coverall features of patentable novelty contained herein as defined in theappended claims.

What I claim is:

l. In combination in a brake and wheel assembly, an axle, a rotatablemember journaled on the axle, a tire, means supporting and securing thetire on -the member, a disc type brake positioned at one side of therotatable member, ring clamping means fastening the brake directly tothe tire supporting and securing means, said disc type brake likewisesurrounding the axle and being anchored thereto, a uniformly expandingring piston for actuating the brake, a plurality of axially extendingsprings normally holding the piston in a non-clamping position androundheaded pins at the ends of the springs to allow relative movementof the springs and the members they engage.

2. In a fluid-pressure brake the combination of a fixed member and arotatable member, a plurality of friction discs alternately connectedwith said fixed member and said rotatable member, an

annular flange carried by said fixed member andhaving an annular chambertherein, an annular piston in said chamber, a pressure plate keyed tosaid fixed member for axial movement and interposed between said pistonand said friction discs for transmitting pressure from the former to thelatter and a sealing ring movable with said piston and pressure plateand having an annular ange engageable with a slot in one of said membersfor excluding foreign material from said chamber and piston.

3. In a fluid-pressure brake the combination of a fixed member and arotatable member, a plurality offrictiondlscs alternately connected withsaid fixed member and said rotatable member, an annular flange carriedby said fixed member and having an annular chamber therein, an annularpiston in said chamber, a pressure plate keyed to said fixed member foraxial movement and interposed between said piston and said frictiondiscs for transmitting pressure from the former to the latter, and asealing ring interposed between said piston and said pressure plate andmovable therewith, said ring bridging said chamber and piston forexcluding foreign material therefrom.

4. In a fluid-pressure brake the combination of a fixed member and arotatable member, a plurality of friction discs alternately connectedwith said fixed member and said rotatable member, an annular flange onsaid fixed member and having an annular chamber therein, an annularpiston in said chamber, a pressure plate keyed to said fixed member foraxial movement and interposed between said piston and said frictiondiscs for transmitting pressure from the former to the latter, and asealing plate interposed between said piston and said pressure plate andmovable therewith, said ring having an annular flange engageable with anannular slot in said first-mentioned flange for excluding foreignmaterial from said chamber and piston.

5. In a fluid-pressure brake the combination of a fixed member and arotatable member, a plurality of friction discs alternately connectedwith said fixed member and said rotatable member, an annular flange onsaid fixed member and having an annular chamber therein, an annularpiston in said chamber, a pressure plate keyed to said fixed member foraxial movement and interposed between said piston and said frictiondiscs for transmitting pressure from the former to the latter and anannular sealing ring interposed between said piston and said pressureplate and movable therewith, said ring having concentric internal andexternal circumferential flanges engageable with annular slots in saidfirst-mentioned flange on opposite sides of said chamber.

6. In a fluid-pressure brake the combination of a fixed axle having awheel rotatably mounted thereon, a sleeve fixed to said axle, aplurality of friction discs alternately connected with said wheel andsleeve, an annular flange on said sleeve and having an annular chambertherein, an annular piston in said chamber, a pressure plate keyed tosaid sleeve for axial movement and interposed between said piston andsaid friction discs for transmitting pressure from the former to thelatter, and a sealing ring interposed between said piston and saidpressure plate and lmovable therewith, said ring bridging said chamdiscsfor transmitting pressure from the former to the latter, and a sealingring interposed between said piston and said pressure plate and movabletherewith, said ring having an annular ange engageable with an annularslot in said rst-mentionedilange for excluding foreign material fromsaid chamber and piston.

8. In a uid-pressure brake the combination of a :dxed axle having awheel rotatably mounted thereon, a sleeve iixed to said axle, aplurality of' friction discs alternately connected with. said wheel andsleeve, an annular flange on said sleeve and having an annular chambertherein, an annular piston in said chamber, a pressure platefirst-mentioned flange on opposite sides of said 10 chamber forexcluding foreign material from, said chamber and piston.

' JAMES C. WAHL.

